The present disclosure relates to the area of analytic control, namely to methods of measuring the concentration of hydroperoxides of alkylaromatic hydrocarbons in industrial streams, such as, for example, the measurement of the concentration of cumene hydroperoxide (CHP) in industrial streams obtained during the production of phenol and acetone by a cumene oxidation method.
The industrial two-stage method of producing phenol and acetone involves continuously oxidizing cumene (isopropylbenzene) with atmospheric oxygen to form an intermediate, cumene hydroperoxide (CHP), in a system of sequential reaction vessels as generally shown by reaction scheme (I). 
As shown in reaction scheme (II), the intermediate CHP then undergoes acid decomposition with a protic acid to form the desired end products, i.e., phenol and acetone. The mixture of phenol and acetone that is formed in the process is separated and purified, usually by rectification on several columns. 
The economic efficiency of phenol and acetone synthesis by the cumene oxidation method depends, for the most part, on the possibilities of achieving the highest possible yields in the cumene oxidation reaction and at the CHP decomposition stage. Another key factor in the production of phenol and acetone by the cumene method is the safety of production, since both reactions, i.e, the oxidation of cumene and the decomposition of CHP, are exothermic. Moreover, CHP, like many other peroxide compounds, is thermally unstable, requires close monitoring of the reaction conditions, and constant monitoring of the current concentration of CHP in the reaction mixture to ensure the necessary level of production safety.
The yield of CHP obtained during continuous oxidation of cumene in a series of reaction vessels depends on its steady-state concentration, which is maintained in each of the reaction vessels. To obtain a high yield of CHP under safe working conditions, samples of the reaction mixture should be taken as often as possible from all cumene oxidation reaction vessels. The samples are typically hand-carried to the laboratory and analyzed for their CHP concentration by titration methods, which ensures the greatest accuracy and reliability. The same method of manual sampling and titration in the analytic laboratory is used for determining the residual concentration of CHP after the stage of its acid decomposition. Since the stage of continuous decomposition of CHP is especially dangerous, laboratory analyses are done around the clock with a frequency of about 6 to about 12 times per day, which translates to about every 2 to about 4 hours.
Typical laboratory analytical methods of determining the CHP content under industrial production conditions include iodometric titration or a wet photometric method, which involves measuring the optical density after an additional reagent is added to the solution containing CHP. However, both of the indicated methods are rather complex, require the use of expensive reagents, and are not practical for continuous industrial processes, e.g., continuous “in process” or “online continuous” applications.
Another method for monitoring the CHP content includes using an “on-line” industrial calorimeter analyzer. However, the method is generally destructive, indirect, and has only been successfully implemented for use in the CHP decomposition stream. The method includes adding sulfuric acid to a small stream taken off the main stream to completely decompose the CHP. In this method, heat is liberated and the corresponding temperature rise is recorded. The CHP concentration is then calculated from the magnitude of the temperature rise. This method is not attractive for commercial use, since it requires a complex apparatus, uses a complex scheme of streams, and requires an added reagent, which needs to be precisely metered to obtain reproducible results as well as requires frequent replenishment. In addition, this method is generally applicable only for very low concentrations of CHP. Moreover, this method is inconvenient for measurements in the stream at the cumene oxidation stage, since the analysis process consumes a significant quantity of CHP.
Other methods propose using a continuous indirect calorimetric method to monitor the conversion of CHP in a two-stage CHP decomposition process. In these processes, a small stream is diverted from the main stream of the CHP decomposition reaction mixture, and measurements are made in a special calorimetric vessel. The quantity of heat liberated is proportional to the CHP concentration. Measurement of the CHP concentration in the stream at the cumene oxidation stage is not proposed.
Accordingly there still remains a need in the art for a direct, non-destructive, automatic, and relatively instantaneous in-stream measurement process for CHP concentration in industrial streams of the production of phenol and acetone using the cumene method.